Joan Rivers is in critical condition after she stopped breathing during surgery on her throat Thursday morning and was rushed to a New York City hospital, according to TMZ.

An emergency call was placed to 911 at 9:39 a.m. The caller said, "We have somebody in either cardiac or respiratory arrest."

TMZ reports that Rivers' heart stopped beating at one point, and it's not clear whether doctors were able to re-start it.

Rivers was reportedly having a procedure on her vocal chords done in a clinic, and stopped breathing during the surgery.

Sources reportedly told the website the 81-year-old was rushed to Mount Sinai hospital in New York and that her daughter Melissa is on her way to New York.

Joan Rivers of E! Television shows off her "diva" necklace during the arrivals for the 44th Annual Grammy Awards on Wednesday, Feb. 27, 2002, at the Staples Center in Los Angeles. (AP Photo/Mark J. Terrill)